Optical measuring devices of this kind, for example, interferometric measuring devices, may be based on the principle of phase analysis, i.e., analyzing the transit time of the light or radiation, or they may be based on the triangulation method (e.g., fringe (strip) projection), where the measurement is made in dependence upon an observation angle and the illumination direction.
Among the interferometric methods, one may distinguish those of classic interferometry (see, e.g., A. Donges, R. Noll in “Lasermesstechnik” (Laser Metrology), Huethig Publishers 1993), of white-light interferometry, where light sources of short coherence length are used (e.g., light-emitting diode, superluminescent diode) (compare P. de Groot, L. Deck, “Surface Profiling by Analysis of White-Light Interferograms in the Spatial Frequency Domain” J. Mod. Opt., vol. 42, no. 2, 389-401, 1995; Th. Dresel, G. Haesler, H. Venzke; “Three-Dimensional Sensing of Rough surfaces by Coherence Radar”, Appl. Opt., vol. 31, no. 7, 919-925, 1992; German Published Patent Application No. 199 48 813 and German Published Patent Application No. 100 15 878) and of heterodyne interferometry (see, e.g., German Published Patent Application No. 197 21 842; H. J. Tiziani, “Optical Methods for Precision Measurements”, Optical and Quantum Electronics, vol. 21, 253-282, 1989; K. Creath, “Temporal Phase Measurement Method” in d. W. Robinson, T. G. Reid: “Interferogram Analysis”, IOP Publishing Bristol 1993; R. Onodera, Y. Ishii, “Two-Wavelength Interferometry That Uses a Fourier Transform Method”, Appl. Opt., vol. 37, no. 34, 7988-7994, 1998).
As discussed, for example, in the two named, non-prepublished German Patent Application Nos. 199 48 813.4 and 100 15 878.1, as well as in the two non-prepublished German Patent Application Nos. 100 33 027.4 and 100 33 028.2, which likewise deal with white-light interferometry, it may be difficult to measure relatively large surface areas, particularly within narrow cavities, quickly and at high resolutions. For example, objects having very small cone angles often may not be measurable using interferometers which work with a plane field of view (flat angular field), since light may not scatter back into the objective. When an endoscope is used, conical or cylindrical surfaces may only be measurable in small segments. Measuring the entire surface may be time-consuming, since many individual segments may need to be measured.